The basic salary schedule for county veterans' service officers, which may be adopted by any board of county commissioners, is:
(1) For counties with population of 50,000 and over, $20,625 a year;
(2) For counties with population of 20,000 to 50,000, $19,250 a year;
(3) For counties with population of 10,000 to 20,000, $16,500 a year;
(4) For counties with population of 5,000 to 10,000, $12,375 a year; and
(5) For counties with population up to 5,000, $8,250 a year.